What exactly do you mean by the rails part Nodsu? And if you attach only one edge, won't it move around in the case and break off or something? I want to know because I want to separate my Raptors from the other two drives coz they get quite hot and I don't want so much heat concentrated together.

There is absolutely no problem with mounting the hard drive from one edge only as long as you use 2 or 3 screws. You will actually reduce noise, because the hard drve won't be transferring that much vibration to the case.